A 28-year-old man, arrested after a fire on board a ferry to the Netherlands, has been bailed.
He was questioned on suspicion of affray after a fire in a cabin on the DFDS MS King Seaways on Saturday night.
A 26-year-old man, arrested on suspicion of arson, remains in police custody.
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Sandiford, a former legal secretary originally from Redcar, was convicted of drug smuggling offences and sentenced to death in 2013.
Durham Crown Court heard that one of the male victims suffered a triple-fractured jaw, while left lying in the gutter, unconscious.